Science to assist policy decisions regarding the prevention of invasive species: testing the survival and growth of quagga mussel in Lake Tahoe

Lead Researchers:

Abstract

Quagga and zebra mussels are establishing in western waterways with large densities in the Colorado Aqueduct system and established populations in North Central California. This invasion is already having profound ecological and economic impacts in these ecosystems. There is a debate amongst scientists and managers on whether the current models that predict the distribution of Dreissenid mussels are accurate. Recently, for example, veligers have been detected in Colorado lakes, some of which have low calcium levels. Furthermore, a study in Lake George (New York) suggests that adult mussels are able to grow under low calcium conditions; however, the veliger recruitment determined from settlement bioassays is likely limiting. What will determine a source versus sink population may not be clear and deserves more attention for western water bodies. Current knowledge suggests that Lake Tahoe can support adult mussels for s short period of time; however, whether juveniles, and thus a reproducing population, can sustain is currently unknown. The proposed research will directly assess the habitat suitability of Lake Tahoe and its watershed to support the establishment of quagga mussel by testing the survivability of veliger to sub-adult stage using Lake Tahoe water. This information will be important for supporting the current efforts related to inspection and washing of boats entering Lake Tahoe.

Relation to Other Research Including SNPLMA Science Projects

Studies in 2008-09 carried out by the University of Nevada- Reno and University of California-Davis showed that adult quagga mussels collected in Lake Mead and maintained in a laboratory setting with low calcium and low chlorophyll water from Lake Tahoe can survive for greater than 50 days. Reproductive analysis showed that there was some evidence of gamete development in these mussels, but findings were inconclusive as to whether mussel populations can maintain themselves in Lake Tahoe conditions. Survival from the veliger stage to adult stage is critical to establishment of dreissenid mussels in any water body, since it indicates the potential for species establishment after introduction. The proposed research is a direct progression from a pilot study funded by the Army Corps of Engineers and the Tahoe Regional Planning Agency in 2009 and from research that has been conducted on the lake's newest invader, the Asian clam. Currently there are multiple projects that address plant, invertebrate, and fish invasions in the nearshore areas of the lake. Recent study of Asian clam beds suggests elevated levels of calcium and substrate from this invader may promote quagga establishment in the lake. This proposed research expands on the latest information regarding clam invasions and will also assist in determining if Asian clam patches and associated clam beds may promote the invasion of quagga mussel. Specifically, this work will build upon the projects, "Development of a risk model to determine the expansion and potential environmental impacts of Asian clams in Lake Tahoe" and "Natural and human limitations to Asian clam distribution and recolonization-factors that impact the management and control in Lake Tahoe."